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I'm stumped and getting nowhere with this question:

Description:

The Air Pollution and Mortality data of 60 cities were collected in a study. 11 can be considered to have high hydrocarbon pollution potential levels. Suppose that two cities are picked at random from the list. (That is, two cities are picked randomly, one after another without replacement.)

Let A be the event that the first city picked has a high hydrocarbon pollution potential level. Let B be the event that the second city picked has a high hydrocarbon pollution potential level.

Question:

"From the physical description of the problem it is possible to directly model P(A), P(A') (complement), P(B|A) and P(B|A')."

So I believe P(A) = 11/60 and P(A') = 49/60.

But I'm unsure of what that last two are? 10/59? 11/59?

NOTE:

The next question is "what is P(A n B) (intersect)?"

Therefore, having this in conjunction with "directly model" means that you're not to use P(AnB) to find P(B|A)

Cheers

JimmyB
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1 Answers1

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If event A is true, then the first city picked is polluted, therefore the other 59 cities contain 10 polluted cities, therefore P(B|A)=10/59 .

If event A' is true, then the first city picked is clean, therefore the other 59 cities contain 11 polluted cities, therefore P(B|A')=11/59 .

So, you were correct in both your guesses.

Erel Segal-Halevi
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